LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034
B.Sc. DEGREE EXAMINATION – STATISTICS
SIXTH SEMESTER – APRIL 2011
ST 6605/ST 6602 - STATISTICAL PROCESS CONTROL
Date : 09-04-2011
Time : 9:00 - 12:00
Dept. No.
Max. : 100 Marks
SECTION A (10 x 2 = 20 Marks )
Answer ALL the questions
1. What do you mean by the term “ cost of quality” ?
2. List the characteristics of TQM derived from its definitions.
3. When do you use Histogram ?
4. What do you mean by frequency distribution ?
5. Mention the purpose of the p-chart.
6. When are C- charts used ?
7. What are control charts ?
8. The following are the and R values of 4 sub-groups of readings:
= 10.2 , 12.1, 10.8 and 10.9
R = 1.1 , 1.3 , 0.9 and 0.8
A2= 0.73 ; D3 = 0 ; D4 = 2.28 ; d2 = 2.059
Find the control limits for chart.
9. What does average total inspection mean?
10. Define Consumer’s Risk and Producer’s Risk.
SECTION B ( 5 x 8 = 40 Marks )
Answer any FIVE questions
11. Explain “Cost of Prevention”.
12. State the benefits of TQM
13. Explain the Box Plot technique.
14. Explain the logic behind the usage of 3 sigma control limits.
15. What are the advantages of variable control charts over attribute control charts?
16. Distinguish between CUSUM chart and Shewhart control chart.
17. What do you mean by Acceptance sampling ? Mention the situations it is most likely to be useful
18. Explain the OC curve for a single sampling plan.
SECTION C ( 2 x 20 = 40 Marks )
Answer any TWO questions
19. a) State the requirements for successful implementation of TQM
b) The following are weekly yield data from a semiconductor fabrication facility. Construct a
Stem and Leaf-plot by selecting the stem values 5, 6,7,8 and 9.
Week : 1 2
3
4
Yield : 58 63 69 72
Week: 21 22 23 24
Yield : 64 68 67 60
5 6
7 8 9
51 79 83 86 85
25 26 27 28 29
59 63 64 52 70
10
78
30
92
11
87
31
75
12 13 14
83 64 73
32 33 34
76 81 74
15 16
81 68
35 36
82 76
17 18 19 20
72 65 91 88
37 38 39 40
75 62 63 92
20. a) What are p and np charts? How they are constructed?
b) Discuss in detail the criteria for lack of control with respect to
-chart.
21. a) Describe the operational aspects of CUSUM charts and the role of V-mask.
b) A certain product has been statistically controlled at a process average of 46 and a standard
deviation of 1.00. The product is presently being sold to two customers who have different
specification requirements. Customer A has established a specification of 48 4.0 for the
product, and customer B has specification of 46 4.0. Use normal distribution and find what
percentage of items go outside the specification limits of (i) Customer A, (ii) Customer B.
22. a) Mention the advantages and disadvantages of Acceptance Sampling.
b) Explain Double Sampling Plan in detail.
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